Lodash _.findKey() Method

Lodash is a JavaScript library that works on the top of underscore.js. Lodash helps in working with arrays, collection, strings, lang, function, objects, numbers etc.

The _.findKey() method is similar to _.find() method except that it returns the key of the first element, predicate returns true for instead of the element itself.

Syntax:

_.findKey(object, predicate)

Parameters: This method accepts two parameters as mentioned above and described below:

• object: It holds the object to inspect every element.
• predicate: It holds the function that the method invoked per iteration.

Return Value: This method returns the key of the matched element else undefined.

Example 1: Here, const _ = require(‘lodash’) is used to import the lodash library in the file.

// Requiring the lodash library
const _ = require("lodash");

// Original array
var users = {
  'meetu':  { 'salary': 36000, 'active': true },
  'teetu':  { 'salary': 40000, 'active': false },
  'seetu':  { 'salary': 10000,  'active': true }
};

// Using the _.findKey() method
let found_elem = _.findKey(users, function(o) { return

o.salary < 40000; });

// Printing the output
console.log(found_elem);

Output:

meetu

Example 2:

// Requiring the lodash library
const _ = require("lodash");

// Original array
var users = {
  'meetu':  { 'salary': 36000, 'active': true },
  'teetu':  { 'salary': 40000, 'active': false },
  'seetu':  { 'salary': 10000,  'active': true }
};

// Using the _.findKey() method
// The `_.matches` iteratee shorthand
let found_elem = _.findKey(users, { 'salary': 10000,

'active': true });

// Printing the output
console.log(found_elem);

Output:

seetu

Example 3:

// Requiring the lodash library
const _ = require("lodash");

// Original array
var users = {
  'meetu':  { 'salary': 36000, 'active': true },
  'teetu':  { 'salary': 40000, 'active': false },
  'seetu':  { 'salary': 10000,  'active': true }
};

// Using the _.findKey() method
// The `_.matchesProperty` iteratee shorthand
let found_elem = _.findKey(users, ['active', false]);

// Printing the output
console.log(found_elem);

Output:

teetu

Example 4:

// Requiring the lodash library
const _ = require("lodash");

// Original array
var users = {
  'meetu':  { 'salary': 36000, 'active': true },
  'teetu':  { 'salary': 40000, 'active': false },
  'seetu':  { 'salary': 10000,  'active': true }
};

// Using the _.findKey() method
// The `_.property` iteratee shorthand
let found_elem = _.findKey(users, 'active');

// Printing the output
console.log(found_elem);

Output:

meetu

Note: This code will not work in normal JavaScript because it requires the library lodash to be installed.